Collagen Telopeptides

The structures of the Type III and V collagen telopeptides have been less studied. However, the NMR study of Type III telopeptides has been reported, and the 22-amino-acid G-terminal telopeptide is extended with a tight turn involving residues 8-11 (Liu et al., 1993). Crosslink analysis reveals connectivity between the G-terminal telopeptide of Type III collagen and the N-terminal helical region of another Type III molecule (Henkel, 1996). 

C6. Christgau, S., Rosenquist, Ch., Alexandersen. P., Bjarnasson, N. H., Ravn, P., et al., Clinical evaluation of the serum CrossLaps one step ELISA, a new assay measuring the serum concentration of bone-derived degradation products of type I collagen telopeptides. Clin. Chem. 44, 2290-2300 (1998). 

A complete physical examination and laboratory analysis are needed to rule out secondary causes and to assess kyphosis and back pain. Laboratory testing may include complete blood count, liver function tests, creatinine, urea nitrogen, calcium, phosphorus, alkaline phosphatase, albumin, thyroid-stimulating hormone, free testosterone, 25-hydroxyvitamin D, and 24-hour urine concentrations of calcium and phosphorus. Urine or serum biomarkers (e.g., cross-linked N-telopeptides of type 1 collagen, osteocalcin) are sometimes used. 

Martini and Wood (2002) tested the bioavailability of 3 different sources of Ca in 12 healthy elderly subjects (9 women and 3 men of mean SEM age 70 3 and 76 6 years, respectively) in a 6-week crossover trial conducted in a Human Study Unit. Each Ca source supplied 1000 mg Ca/day and was ingested for 1 week with meals (as 500 mg Ca 2x/day), thus contributing to a high-Ca intake (1300 mg Ca/day). A low-Ca intake (300 mg Ca/day strictly from the basal diet) was adhered to for 1 week in-between each treatment. The Ca sources included skim milk, CCM-fortified OJ, and a dietary supplement of CaCOa. Assessment parameters were indirect measures predicted to reflect the relative bioavailability of Ca postprandially via an acute PTH suppression test (hourly for 4h). Longer-term responses to Ca supplementation were assessed via a number of urinary and serum hormone, mineral, and bone resorption biomarkers (i.e., vitamin D, Ca, phosphorus, and collagen t) e 1 N-telopeptide cross-links). 

Type I collagen carboxy-terminal telopeptide (ICTP)... 

Blood Alkaline phosphatase (bone-specific) Osteocalcin Procollagen type I carboxy-terminal propeptide (PICP) Procollagen type I amino-terminal propeptide (PINP) Procollagen type III amino-terminal propeptide (PIIINP) Blood Acid phosphatase (acid-resistant) Type I collagen carboxy-terminal telopeptide (ICTP) Urine Calcium Hydroxyproline Cross-linked peptides (pyridinium and deoxypyridinoline)... 

In 70 postmenopausal women with completely resected breast cancers who were disease-free after taking tamoxifen for 2—3 years, a switch to exemestane resulted in increases in serum bone alkaline phosphatase and the carboxy-terminal telopeptide of type I collagen and a fall in parathormone bone mineral density worsened (28). 

Helseth, D. L., and Veis, A. (1981). Collagen self-assembly in vitro. Differentiating specific telopeptide dependent interactions using selective enzyme modification and the addition of free amino telopeptide./. Biol. Chem. 256, 7118-7128. 

Henkel, W. (1996). Cross-link analysis of the C-telopeptide domain from type III collagen. Biochem. J. 318, 497-503. 

McBride, D.J., Choe, V., Shapiro, J. R., and Brodsky, B. (1997). Altered collagen structure in mouse tail tendon lacking the alpha 2(1) chain./. Mol. Biol. 270, 275-284. Malone, J. P., George, A., and Veis, A. (2004). Type I collagen N-telopeptides adopt an ordered structure when docked to their helix receptor during fibrillogenesis. 

Orgel, J. P., Wess, T. J., and Miller, A. (2000). The in situ conformation and axial location of the intermolecular cross-linked non-helical telopeptides of type I collagen. Struct. Fold. Des. 8, 137-142. 

Ortolani, F., Giordano, M., and Marchini, M. (2000). A model for type II collagen fibrils Distinctive D-band patterns in native and reconstituted fibrils compared with sequence data for helix and telopeptide domains. Biopolymers 54, 448-463. 

Vitagliano, L., Nemethy, G., Zagari, A., and Scheraga, H. A. (1995). Structure of the type-I collagen molecule based on conformational energy computations The triple-stranded helix and the N-terminal telopeptide. / Mol. Biol. 247, 69-80. 

The free carbonyl residue can further condense with a histidyl group of another polypeptide chain to give a more complex cross-link. Schiff base formation, illustrated in Figure 8.4, involves an allysine residue at either the C- or N-terminal telopeptide and an uncharged lysine or hydroxylysine residue of another properly juxtaposed tropocollagen molecule. Such bonds are therefore intermolecular. Several other types of covalent cross-links are possible in collagens. They almost always involve lysine, allysine, hydroxylysine, hydroxyal-lysine, or histidine. 

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